Tyre/road noise frequency spectra analyses based on CPX measurement with six microphones

Road traffic noise is affected by many factors, the road surface being one of them. The CPX method (ISO 11819-2) is the method used to measure tyre/road noise, i.e. noise generated by tyre-surface contact. Up to six microphones are positioned around reference tyre (ISO 11819-3) in specified positions as the standard requires. Two microphones are mandatory; four are optional. Conventional stone mastic asphalt, low-noise pavement, exposed aggregate cement concrete and cobblestones were measured by the CPX method using six microphones at a velocity of 80 km/h. Tyre/road noise frequency spectra from each microphone will be shown in this paper. Presented results should be used to discussion about positions or necessity of mandatory and optional microphones.